Quadrature oscillator and methods thereof

ABSTRACT

A quadrature oscillator includes a master tuned oscillator and two injection-locked slave tuned oscillators.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/401,024, filed Mar. 28, 2003.

BACKGROUND OF THE INVENTION

Radio frequency (RF) transceivers may use quadrature modulation forhigher spectral efficiency. The quadrature signals that are used formodulation and demodulation directly affect the performance of thetransceiver and thus it is desirable that the quadrature signals beprecise and have a low phase noise. Consequently, these signals may begenerated locally at the transceiver.

In some conventional transceivers, an oscillator is used to produce aninitial frequency at four times the desired frequency of the quadraturesignals. The initial frequency is then divided down using at least twostages of digital dividers.

It is well known that generating a high frequency signal may bedifficult due to device parasitic capacitances and inductances in theprocess. This, and the fact the in some conventional transceivers, thesource oscillator oscillates at a frequency four times higher than thedesired frequency of the quadrature signals, currently limit thequadrature signal frequencies that can be generated. High frequencysignals also tend to have a high phase noise.

It is also known that digital dividers are high bandwidth devices, andconsequently, the quadrature signals at their output may have more phasenoise than the original signal before division.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanied drawings in which:

FIG. 1 is a simplified block-diagram illustration of an exemplarycommunication system, in accordance with some embodiments of the presentinvention;

FIG. 2A is a simplified block-diagram illustration of a quadratureoscillator, in accordance with some embodiments of the presentinvention;

FIG. 2B is a simplified exemplary illustration of waveforms of signalsin the quadrature oscillator of FIG. 2A; and

FIGS. 3-10 are schematic illustration of quadrature oscillators, inaccordance with various embodiments of the present invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However it will be understood by those of ordinary skill in the art thatthe present invention may be practiced without these specific details.In other instances, well-known methods, procedures, components andcircuits have not been described in detail so as not to obscure thepresent invention.

It should be understood that the present invention may be used in avariety of applications. Although the present invention is not limitedin this respect, the circuit disclosed herein may be used in manyapparatuses such as the transmitters and receivers of a radio system.Radio systems intended to be included within the scope of the presentinvention include, by way of example only, cellular radio telephonecommunication systems, wireless local area networks that meet theexisting 802.11a, b, g, and future high data-rate versions of the above,two-way radio communication systems, one-way pagers, two-way pagers,personal communication systems (PCS) and the like.

Types of cellular radiotelephone communication systems intended to bewithin the scope of the present invention include, although not limitedto, Direct Sequence-Code Division Multiple Access (DS-CDMA) cellularradiotelephone communication systems, Global System for MobileCommunications (GSM) cellular radiotelephone systems, North AmericanDigital Cellular (NADC) cellular radiotelephone systems, Time DivisionMultiple Access (TDMA) systems, Extended-TDMA (E-TDMA) cellularradiotelephone systems, wideband CDMA (WCDMA), General Packet RadioService (GPRS) systems, Enhanced Data for GSM Evolution (EDGE) systems,3.5G and 4G systems.

FIG. 1 is a simplified block-diagram illustration of an exemplarycommunication system, in accordance with some embodiments of the presentinvention. A communication device 100 is able to communicate with acommunication device 110 over a communication channel 120. It will beappreciated by persons of ordinary skill in the art that a quadratureoscillator according to embodiments of the present invention may bepresent in communication device 100 only or in communication device 110only or in both communication devices 100 and 110. The followingdescription is based on the example of both communication devicescomprising a quadrature oscillator according to one or another of theembodiments of the present invention, although the present invention isnot limited in this respect.

Although the present invention is not limited in this respect, thesystem shown in FIG. 1 may be part of a cellular communication system,with one of communication devices 100, 110 being a base station and theother a mobile station or with both apparatuses 100, 110 being mobilestations, a pager communication system, a personal digital assistant anda server, etc. Communication devices 100 and 110 may each comprise aradio frequency antenna 102, which may be, for example, a dipole antennaor any other suitable radio frequency antenna.

Communication device 100 may comprise a transmitter 108 that maycomprise a modulator 103 and a quadrature oscillator 109. Modulator 103may modulate and upconvert a data signal 101 using quadrature signals105 and 106 generated by quadrature oscillator 109 to produce anupconverted modulated data signal 104, which after amplification by apower amplifier (not shown) may then be transmitted by RF antenna 102over communication channel 120.

Communication device 110 may comprise a receiver 118 that may comprise ademodulator 113 and a quadrature oscillator, referenced 109 to indicatethat it may be similar to quadrature oscillator 109 of transmitter 108.Receiver 118 may receive a modulated data signal 111 from communicationchannel 120 via RF antenna 102, which may be demodulated anddownconverted by demodulator 113 using quadrature signals 105 and 106generated by quadrature oscillator 109.

It will be appreciated by persons of ordinary skill in the art thatcommunication devices 100 and 110, and in particular transmitter 108 andreceiver 118, may comprise additional components that are not shown inFIG. 1 so as not to obscure the invention.

FIG. 2A is a simplified block-diagram illustration of an exemplaryquadrature oscillator, in accordance with some embodiments of thepresent invention. Quadrature oscillator 209 may comprise a mastertuned-oscillator 200 and two slave tuned-oscillators 201 and 202.

The master tuned-oscillator 200 may oscillate at its naturalself-resonant frequency f_(M), which may be selectable from a range offrequencies, producing two signals 203 and 204. Both signals may have afrequency 2 f_(O) and a phase difference of π radians therebetween.

Slave tuned-oscillators 201 and 202 may have natural self-resonantfrequencies f_(S1) and f_(S2), respectively. Slave tuned-oscillator 201(202) may comprise an input node 207 (208) having the property that whenslave tuned-oscillator 201 (202) oscillates at its natural self-resonantfrequency, only even harmonics of the natural self-resonant frequencycan exist at this input node 207 (208). Slave tuned-oscillator 201 (202)may also comprise an optional input node 217 (218) having the propertythat when slave tuned-oscillator 201 (202) oscillates at its naturalself-resonant frequency, only even harmonics of the naturalself-resonant frequency can exist at this input node 217 (218).Moreover, the signal at input node 217 (218) may have a phase differenceof π radians from the signal at node 207 (208).

However, if a periodic signal having certain characteristics is injectedinto input node 207 (208), slave tuned-oscillator 201 (202) and itsoutput signal 205 (206) may oscillate at half of the injected signal'sfrequency and not at its natural self-resonant frequency f_(S1)(f_(S2)). Moreover, output signal 205 (206) may maintain phase relationswith the signal injected at 207 (208).

If a periodic signal having certain characteristics is injected intoinput node 207 (208), and in addition, a periodic signal having similarcharacteristics and having a phase difference of π radians from thesignal at node 207 (208) is injected into input node 217 (218), slavetuned-oscillator 201 (202) and its output signal 205 (206) may oscillateat half of the injection signal's frequency and not at its naturalself-resonant frequency f_(S1) (f_(S2)). This oscillation may be moreimmune to noise than the oscillation induced by having an injectedsignal only at one input node. Moreover, output signal 205 (206) maymaintain phase relations with the signal injected at 207 (208).Consequently, a period of the signal at 205 (206) may contain twoperiods of the signal at 207 (208).

Signal 203, having a frequency of 2 f_(O), may be injected into node 207of slave tuned-oscillator 201 through an optional matching network 210.If slave tuned-oscillator 201 is tuned to have its resonant frequencyf_(S1) sufficiently close, for example, within an injection-lockingrange, to f_(O), and the amplitude of signal 203 is within anappropriate range, then slave tuned-oscillator 201 may oscillate at halfof the frequency of signal 203, namely at f_(O). Slave tuned-oscillator201 may then generate output signal 205 at frequency f_(O) and maintaina phase relation with signal 203. In other words, slave tuned-oscillator201 is ‘locked’ to signal 203.

Similarly, signal 204, having a frequency of 2 f_(O), may be injectedinto node 208 of slave tuned-oscillator 202 through optional matchingnetwork 210. If slave tuned-oscillator 202 is tuned to have its naturalself-resonant frequency f_(S2) sufficiently close, for example, withinan injection-locking range, to f_(O), and the amplitude of signal 204 iswithin an appropriate range, then slave tuned-oscillator 202 mayoscillate at half of the frequency of signal 204, namely at f_(O). Slavetuned-oscillator 202 may then generate output signal 206 at frequencyf_(O) and maintain a phase relation with signal 204. In other words,slave tuned-oscillator 202 is ‘locked’ to signal 204.

In addition, signal 203 may be injected into node 218 of slavetuned-oscillator 202 through optional matching network 210, and signal204 may be injected into node 217 of slave tuned-oscillator 201 throughoptional matching network 210.

Reference is now made briefly to FIG. 2B, which is a simplifiedexemplary illustration of a waveform of signals 203, 204, 205 and 206 ofFIG. 2A, when slave tuned-oscillator 201 is locked to signal 203 andslave tuned-oscillator 202 is locked to signal 204. Signals 203 and 204may have a period T and may be opposite in direction, reflecting afrequency of 2 f_(O) and a phase difference of π radians. Signals 205and 206 may have a period 2T, reflecting a frequency of f_(O).

Signal 205 may maintain phase relations with signal 203, havingdirection changes 240 occurring T1 seconds after low-to-high changes 245of signal 203. Signal 206 may maintain phase relations with signal 204,having direction changes 250 occurring T2 seconds after low-to-highchanges 255 of signal 204. When slave tuned-oscillator 201 is locked tosignal 203 and slave tuned-oscillator 202 is locked to signal 204, thenT1 equals T2, resulting in phase quadrature, that is, a phase differenceof π/2 radians between signals 205 and 206. Since signals 205 and 206are generated by two tuned circuits that are locked together, the phasenoise may be reduced by a factor related to the square of the qualityfactor of the resonant circuits (“tanks”).

In FIGS. 3-10, quadrature oscillators according to various exemplaryembodiments of the present invention will now be described. Theseexemplary quadrature oscillators include exemplary embodiments of mastertuned-oscillators and slave tuned-oscillators corresponding to themaster tuned-oscillators and slave tuned-oscillators of FIG. 2A.

In FIGS. 3, 4, 5, 7, and 8, a master tuned-oscillator is coupled toslave tuned-oscillators with single-ended inputs, possibly usingappropriate matching networks. In FIGS. 6, 9, and 10, a mastertuned-oscillator is coupled to slave tuned-oscillators with differentialinputs.

The master tuned-oscillators illustrated in FIGS. 3, 7, and 10 are tunedto oscillate at 2 f_(O) in order to generate output signals 203 and 204oscillating at 2 f_(O). In contrast, in FIGS. 4, 5, 6, 8 and 9, sinceoutput signals 203 and 204 are generated at second-harmonic nodes,master tuned-oscillator is tuned to oscillate at f_(O) to produce outputsignals 203 and 204 oscillating at 2 f_(O).

FIG. 3 is a schematic illustration of a quadrature oscillator 309, inaccordance with some embodiments of the present invention. Quadratureoscillator 309 may comprise a master tuned-oscillator 300 and slavetuned-oscillators 301 and 302, and may optionally comprise a matchingnetwork 310.

Master tuned-oscillator 300 may comprise two pairs of cross-coupledtransistors 316, a tank 314, and a transistor 318. Tank 314 may comprisecapacitors 311 and inductors 312 connected in parallel. The naturalself-resonant frequency f_(M) of master tuned-oscillator 300 may bedetermined by the properties of capacitors 311 and inductors 312.Inductors 312 may have a fixed inductance, while capacitors 311 may bevariable and controlled for the purpose of tuning the naturalself-resonant frequency f_(M). Cross-coupled transistors 316 may createa negative resistance path to cancel out any losses in tank 314.Transistor 318 may be a tail current source, receiving a biasing signal320 at its gate 322. A node 324 may have the property that only evenharmonics of the natural self-resonant frequency f_(M) can exist at thisnode.

Natural self-resonant frequency f_(M) of master tuned-oscillator 300 maybe tuned to be 2 f_(O), namely, signals 203 and 204 may be of frequency2 f_(O).

Slave tuned-oscillator 301 (302) may comprise two pairs of cross-coupledtransistors 336 (356), a tank 334 (354) and a transistor 338 (358). Tank334 (354) may comprise capacitors 330 (350) and inductors 332 (352)connected in parallel. The natural self-resonant frequency f_(S1)(f_(S2)) of slave tuned-oscillator 301 (302) may be determined by theproperties of capacitors 330 (350) and inductors 332 (352). Inductors332 (352) may have a fixed inductance, while capacitors 330 (350) may bevariable and controlled for the purpose of tuning the naturalself-resonant frequency f_(S1) (f_(S2)). Cross-coupled transistors 336(356) may create a negative resistance path to cancel out any losses intank 334 (354). Transistor 338 (358) may be a tail current sourcereceiving a biasing signal 340 (360) at its gate 342 (362). Naturalself-resonant frequency f_(S1) (f_(S2)) of slave tuned-oscillators 301(302) may be tuned to be sufficiently close to f_(O). Moreover, thesignal injected at an input node 207 (208) may have the appropriateamplitude, and consequently slave tuned-oscillator 301 (302) may lock tothe signal at input node 207 (208).

A single-ended connection scheme, an exemplary embodiment of which isshown by matching network 310, may be used to couple mastertuned-oscillator 300 and slave tuned-oscillators 301 and 302. Matchingnetwork 310 may couple signal 203 to input node 207 and signal 204 toinput node 208. Capacitors 370 of matching network 310 may block thedirect current (DC) components and pass the alternate current (AC)components of signals 203 and 204. Although the present invention is notlimited in this respect, capacitors 370 may be Metal-Insulator-Metal(MiM) capacitors available as an add-on forComplementary-Metal-Oxide-Semiconductor (CMOS), vertical meshMetal-Metal capacitors. Matching network 310 may optionally comprisebuffers 372 coupled to capacitors 370 to minimize kickback of signalsinto master tuned-oscillator 300.

FIG. 4 is a schematic illustration of a quadrature oscillator 409, inaccordance with some embodiments of the present invention. Quadratureoscillator 409 may comprise a master tuned-oscillator 400 and slavetuned-oscillators 301 and 302, and may optionally comprise matchingnetwork 310.

Master tuned-oscillator 400 is similar to master tuned-oscillator 300,and may have differences as described below.

Master tuned-oscillator 400 may contain a tail current source transistor410 that may require an additional biasing signal 414 and may create anode 412. As with node 324, node 412 may have the property that onlyeven harmonics of the natural self-resonant frequency f_(M) can exist atthis node. Moreover, the signal at node 412 may have a phase differenceof π radians from the signal at node 324.

Provided that master tuned-oscillator 400 is tuned to oscillate atfrequency f_(M)=f_(O), nodes 324 and 412 may develop the second harmonicof f_(M), namely 2 f_(O), and may oscillate with a phase difference of πradians. Consequently nodes 324 and 412 may be used as sources forsignals 204 and 203, respectively.

FIG. 5 is a schematic illustration of a quadrature oscillator 509, inaccordance with some embodiments of the present invention. Quadratureoscillator 509 may comprise master tuned-oscillator 400 and slave tunedoscillators 501 and 502, and may optionally comprise matching network310.

Slave tuned oscillators 501 and 502 are similar to slavetuned-oscillators 301 and 302, respectively, and may have differences asdescribed below.

Slave tuned-oscillator 501 (502) may contain a tail current sourcetransistor 510 (512) that may receive a biasing signal at an input node514 (516) and may create a node 507 (508). Node 507 (508) may havesimilar properties to those of node 207 (208), namely, if slavetuned-oscillator 501 (502) oscillates in its natural self-resonantfrequency f_(S1) (f_(S2)), only even harmonics of the naturalself-resonant frequency can exist at this node. Moreover, the signal atnode 507 (508) may have a phase difference of π radians from the signalat node 207 (208).

When a periodic signal of 2 f_(O) frequency and adequate amplitude isinjected into node 207 (208), node 507 (508) may oscillate at frequency2 f_(O) and may have a phase that is π radians apart from the injectedsignal at node 207 (208).

It will be appreciated by persons of ordinary skill in the art that thearchitecture of slave tuned-oscillators 501 and 502 is similar to thatof master tuned-oscillator 400. Consequently, the total phase noiseassociated with quadrature oscillator 509 may be reduced relative tothat associated with quadrature oscillator 409.

FIG. 6 is a schematic illustration of a quadrature oscillator 609, inaccordance with some embodiments of the present invention. Quadratureoscillator 609 may comprise master tuned-oscillator 400 and slavetuned-oscillators 501 and 502, and may optionally comprise a matchingnetwork 610.

A differential connection scheme, an exemplary embodiment of which isshown by matching network 610, may be used to couple mastertuned-oscillator 400 and slave tuned-oscillators 501 and 502. Matchingnetwork 610 may couple signal 203 to input node 207 of slavetuned-oscillator 501 and to input node 508 of slave tuned-oscillator502, and may also couple signal 204 to input node 208 of slavetuned-oscillator 502 and to input node 507 of slave tuned-oscillator501.

Matching network 610 may comprise capacitors 370 for input nodes 207 and208, and capacitors 614 for input nodes 507 and 508. Matching network610 may also optionally comprise buffers 372 for input nodes 207 and208, and buffers 612 for input nodes 507 and 508.

When a periodic signal of 2 f_(O) frequency and adequate amplitude isinjected into node 207 (208), node 507 (508) may oscillate at frequency2 f_(O) and may have a phase that is π radians apart from the injectedsignal at node 207 (208).

Furthermore, when a periodic signal of 2 f_(O) frequency and adequateamplitude is injected into node 507 (508), slave tuned-oscillator 501(502) and its output signal 205 (206) may oscillate at half of theinjection signal's frequency and not at its natural self-resonantfrequency f_(S1) (f_(S2)), and may maintain phase relations with thesignal injected at node 507 (508).

Furthermore, when periodic signals of 2 f_(O) frequency, adequateamplitudes and a phase difference of π radians are injected into nodes207 and 507 (208 and 508), slave tuned-oscillator 501 (502) mayoscillate at f_(O) frequency and maintain phase relations with theinjected signals. This behavior is the same, but more immune to noise,than in the case of a signal injected solely into node 207 (208) or 507(508).

It will be appreciated by persons of ordinary skill in the art thatsince quadrature oscillator 609 incorporates a differential connectionscheme, the total phase noise associated with quadrature oscillator 609may be less than that of quadrature oscillator 509, which incorporates asingle-ended connection scheme.

FIG. 7 is a schematic illustration of a quadrature oscillator 709, inaccordance with some embodiments of the present invention. Quadratureoscillator 709 may comprise master tuned-oscillator 300 and slavetuned-oscillators 701 and 702, and may optionally comprise a matchingnetwork 710.

Gate 342 (362) of tail current source transistor 338 (358) may be usedat tuned oscillator 701 (702) as input node 207 (208). The amplitude ofthe signal at input node 207 (208) may be smaller than the minimumamplitude required to force slave tuned-oscillator 701 (702) tooscillate at f_(O). (In this embodiment, the natural self-resonantfrequency f_(M) of master tuned-oscillator 300 may be tuned to be 2f_(O), namely, signals 203 and 204 may be of frequency 2 f_(O).) Slavetuned oscillator 701 (702) may therefore optionally comprise a shuntresonant circuit 730 (732), tuned to 2 f_(O) frequency. Shunt resonantcircuit 730 (732) may be coupled to a node 770 (772), matching theamplitude requirements of slave tuned-oscillator 701 (702) to theamplitude of the signal at input node 207 (208).

A single-ended connection scheme, an exemplary embodiment of which isshown by matching network 710, may be used to couple mastertuned-oscillator 300 and slave tuned-oscillators 701 and 702. Matchingnetwork 710 comprising capacitors 370 may couple signal 203 to inputnode 207 and signal 204 to input node 208. In contrast with matchingnetwork 310 of FIG. 3, matching network 710 may not comprise buffers 372since the input impedance of gates 342 and 362 may be high. Matchingnetwork 710 may comprise resistors 711 and 712 to inject DC biasingsignals 722 and 724 to the gates 342 and 362 of tail current sourcetransistors 338 and 358, respectively.

FIG. 8 is a schematic illustration of a quadrature oscillator 809, inaccordance with some embodiments of the present invention. Quadratureoscillator 809 may comprise master tuned-oscillator 400 and slavetuned-oscillators 801 and 802, and may optionally comprise matchingnetwork 710.

Slave tuned oscillators 801 and 802 are similar to slavetuned-oscillators 701 and 702 of FIG. 7 respectively, and may havedifferences as described below.

Slave tuned-oscillator 801 (802) may contain tail current sourcetransistor 510 (512) that may require an additional biasing signal atnode 514 (516) and may create a node 507 (508)

As in quadrature oscillator 509 of FIG. 5, the architecture of slavetuned-oscillators 801 and 802 is similar to that of mastertuned-oscillator 400. Consequently, the total phase noise associatedwith quadrature oscillator 809 may be reduced.

FIG. 9 is a schematic illustration of a quadrature oscillator 909, inaccordance with some embodiments of the present invention. Quadratureoscillator 909 may comprise master tuned-oscillator 400 and slavetuned-oscillators 901 and 902, and may optionally comprise a matchingnetwork 910.

Slave tuned oscillators 901 and 902 are similar to slavetuned-oscillators 801 and 802, respectively, and may have differences asdescribed below.

A shunt resonant circuit 930, that may be similar to shunt resonantcircuit 730, may be coupled to node 507 of slave tuned-oscillator 901. Ashunt resonant circuit 932, that may be similar to shunt resonantcircuit 732, may be coupled to node 508 of slave tuned-oscillator 902.

A differential connection scheme, an exemplary embodiment of which isshown by matching network 910, may be used to couple mastertuned-oscillator 400 and slave tuned-oscillators 901 and 902. Matchingnetwork 910 may couple signal 203 to input node 207 of slavetuned-oscillator 901 and to input node 516 of slave tuned-oscillator902, and may also couple signal 204 to input node 208 of slavetuned-oscillator 902 and to input node 514 of slave tuned-oscillator901.

Matching network 910 may comprise capacitors 370 for input nodes 207 and208, and may also comprise resistors 711 and 712 to couple DC biasingsignals 722 and 724 to the gates 342 and 362 of tail current sourcetransistors 338 and 358, respectively. Moreover, matching network 910may comprise capacitors 914 for input nodes 514 and 516, and may alsocomprise resistors 920 and 922 to couple DC biasing signals 924 and 926to the gates of tail current source transistors 510 and 512,respectively.

It will be appreciated by persons of ordinary skill in the art thatsince quadrature oscillator 909 incorporates a differential connectionscheme, the total phase noise associated with quadrature oscillator 909may be less than that of quadrature oscillator 809, which incorporates asingle-ended connection scheme.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. As onenon-limiting example of these many modifications and changes, aquadrature oscillator 1009 shown in FIG. 10 may comprise mastertuned-oscillator 300 and slave tuned-oscillators 501 and 502, and mayoptionally comprise matching network 610. It is, therefore, to beunderstood that the appended claims are intended to cover all suchmodifications and changes as fall within the true spirit of theinvention.

1. A method comprising: generating quadrature signals from substantiallyanti-phase output signals of a source oscillator oscillating at afrequency, said output signals having substantially twice saidfrequency, said quadrature signals having substantially half saidfrequency and having a phase difference therebetween of substantiallyπ/2 radians.
 2. The method of claim 1, wherein generating saidquadrature signals comprises: tuning slave oscillators coupled to saidsource oscillator to have a natural self-resonant frequency within aninjection-locking range to said frequency.
 3. The method of claim 1,wherein generating said quadrature signals comprises: injecting saidoutput signals to single-ended inputs of tuned slave oscillators.
 4. Themethod of claim 1, wherein generating said quadrature signals comprises:injecting said output signals to differential inputs of tuned slaveoscillators.
 5. An apparatus comprising: a quadrature oscillatorincluding at least a source oscillator able to oscillate at a frequencyand to produce substantially anti-phase output signals at saidfrequency, said quadrature oscillator able to generate quadraturesignals from said output signals, said quadrature signals havingsubstantially half said frequency and having a phase differencetherebetween of substantially π/2 radians.
 6. The apparatus of claim 5,wherein said quadrature oscillator further includes two slaveoscillators having input nodes coupled to output nodes of said sourceoscillator.
 7. The apparatus of claim 6, wherein said input nodes arecoupled to said output nodes via a single-ended connection scheme. 8.The apparatus of claim 6, wherein said input nodes are coupled to saidoutput nodes via a differential connection scheme.
 9. The apparatus ofclaim 6, wherein the architecture of each of said slave oscillators issimilar to the architecture of said source oscillator.
 10. The apparatusof claim 6, wherein said slave oscillators are tuned oscillators. 11.The apparatus of claim 6, wherein at least one of said slave oscillatorsincludes at least one shunt resonant circuit tuned to twice saidfrequency.
 12. The apparatus of claim 6, further comprising a matchingnetwork coupling said slave oscillators to said source oscillator. 13.The apparatus of claim 5, wherein said source oscillator is a tunedoscillator.
 14. A communication device comprising: a dipole antenna; anda quadrature oscillator including at least a source oscillator able tooscillate at a frequency and to produce substantially anti-phase outputsignals at said frequency, said quadrature oscillator able to generatequadrature signals from said output signals, said quadrature signalshaving substantially half said frequency and having a phase differencetherebetween of substantially π/2 radians.
 15. The communication deviceof claim 14, wherein said quadrature oscillator further includes twoslave oscillators having input nodes coupled to output nodes of saidsource oscillator.
 16. The communication device of claim 14, whereinsaid communication device is a mobile station.
 17. A communicationsystem comprising: a first communication device; and a secondcommunication device able to communicate with said first communicationdevice via a communication channel, wherein at least one of said firstcommunication device and said second communication device comprises: aquadrature oscillator including at least a source oscillator able tooscillate at a frequency and to produce substantially anti-phase outputsignals at said frequency, said quadrature oscillator able to generatequadrature signals from said output signals, said quadrature signalshaving substantially half said frequency and having a phase differencetherebetween of substantially π/2 radians.
 18. The communication systemof claim 17, wherein said quadrature oscillator further includes twoslave oscillators having input nodes coupled to output nodes of saidsource oscillator.
 19. The communication system of claim 18, whereinsaid quadrature oscillator further comprises a matching network couplingsaid slave oscillators to said source oscillator.